The main types of memory that are currently widely in use are dynamic random access memory (DRAM) and flash memories. DRAMs are volatile memories and consume a large amount of power at least because they are periodically refreshed. Flash memories are non-volatile memories but perform write operations at low speed and are typically limited in the number of rewrite operations they can perform.
In order to overcome these problems, next-generation memories including phase-change random access memory (PRAM), magnetoresistive random access memory (MRAM), and ferro-electric random access memory (FRAM) are being developed and are receiving much attention.
These next-generation memories are generally able to memorize information by a change in resistance according to a phase change, the control of electron spins, and the control of polarization of a ferroelectric material. In order to fabricate such memories, materials having these features are generally formed at a predetermined location on a device. Recently, research has been conducted into memory devices having a confined structure in order to consume a small amount of power and displaying good performance while maintaining the unique characteristics of these materials
Confined-structure memory devices denote memory devices in which via holes are formed within insulation layers and filled with materials having such features as described above. These materials may be formed by chemical vapor deposition (CVD). However, it is usually difficult to fabricate confined-structure memory devices having good performance by using CVD.
In other words, these materials are deposited in a crystalline structure at a high temperature using CVD. FIG. 1A is a conceptual diagram illustrating voids formed when a material layer is formed within a via hole according to the conventional art. Referring to FIG. 1A, since the material layer is formed by depositing the material in a polycrystalline structure, a plurality of voids 20 may be formed within a via hole 10. Formation of the voids 20 may result in the manufacture of defective memory devices. This problem can be seen from plugs formed by CVD as illustrated in FIG. 1B. Arrows in FIG. 1B indicate plugs having voids formed therein.
Accordingly, a method of depositing a material having a memorization characteristic with limited formation of voids within a via hole is desired.